Twinning, or duplexing, plastic insulated wires



March 25, 1958 M. c. HENGEL ETAL TWINNING, 0R DUPLEXING, PLASTIC INSULATED WIRES Filed Sept. 17, 1953 ATTORN EY United States Patent TWINNING, 0R DUPLEXING, PLASTIC INSULATED WIRES Mathew Carl Hengel, Latrobe, and James Harvey Steele, Belle Vernon, Pa., assignors to American Cyanamid Company, New York, N. Y., a corporation of Maine Application September 17, 1953, Serial No. 380,774 7 Claims. (Cl. 154-2.24)

This invention relates generally to electrical cables. More particularly the invention relates to the making of cables composed of a plurality of individual strands of insulation-bonded wire.

Many different methods for making electrical cables have been used in the past. In one method, individual strands of wire are wrapped or coated with insulation of some kind, and then the insulated strands are gathered into a bundle. The bundle is then wrapped or coated with insulation in a separate step to produce the desired cable.

In another method, individual strands of wire are forced through a die. At the same time a suitable insulation is extruded under pressure through the die so that the individual strands of wire are simultaneously insulated from each other and bound into a unified whole. These extrusion processes have been used particularly to form duplex cables.

It is often desirable in an electrical cable to be able to identify individual strands of wire at each end of the cable. This is sometimes done by coloring the wrapping or insulation on one or more of the individual strands of wire. But in extrusion processes, color coding can only be accomplished with difiiculty. Differently colored dyes tend to bleed from one location to another.

Thus there is a need for a simple process for making electrical cable, coded or plain, without the use of pres sure dies and without complex coating and wrapping machinery.

It is the principal object of the present invention to supply this need.

, Surprisingly, the objects of the present invention have been attained by contacting together at least two insulated wires, at least one of which being coated with a plastic insulation in a tacky condition. The bundle of wires may then be cooled or cured resulting in permanent adhesion at the point at which the wires were contacted. This not only eliminates the extrusion processes currently used in cable making, but produces a cable having many economic advantages.

The present invention will be more completely described with reference to the accompanying drawings in which:

Fig. l is a perspective elevation partly in section of a simplified coating and drying device for carrying out the present invention;

Fig. 2 is an enlarged perspective elevation of a means for bringing two wires into contact;

Fig. 3 is a perspective elevation showing an alternative type of device for carrying out the present invention;

Fig. 4 shows enlarged cross sectional views of one type of duplex cable prepared by the present invention;

Fig. 5 shows an enlarged cross section of another type of duplex cable; and

Fig. 6 shows a cross section of the enlarged four-wire cable of the present invention.

Although the present invention contemplates electrical 2,828,234 Patented Mar. 25, 1958 cables containing a large number of wires if desired, the illustrated discussion of the invention will be concerned with only two wires. Cable containing more than two wires may be as readily prepared as those that merely contain two.

In the present invention, as shown in Fig. l, a wire 1 passes up through a nozzle 2 into an applicator pot 3. The pot 3 contains a bath 4 of the material to be used as insulation. The wire 1 then passes through the wiper or die 5 which serves to wipe off the excess plastic from the bath 4. The coating may be thick or thin. It is only necessary that the coating retain its shape until it is treated further on in the process. If the cable is to be a duplex cable such as is used with electric detonators and ignitors, then it is preferable that the final coating measure about 3 to 8 mils in thickness.

The plastic coated wire 6 then passes into a contacting or constrictive means 7. The constrictive means 7 brings the wire 6 into just sufficient physical contact with the wire 8 that the wet insulation on wire 6 flows slightly on to wire 8. Wire 8 has previously been coated with a plastic insulation. Since its insulation is dry, it is guided through the bath 4 by channel 9 in order that it will be in a dry condition when it passes over the guiding pulley 10.

The contacting or constrictive means 7 in Fig. 1 is shown enlarged in Fig. 2. It is a pulley having a groove whose size is suflicient to carry the wire 8. Due to the natural rigidity of the wires the point of contact between them lies a little above the point where wire 8 passes over constrictive means 7. Alternatively, the constrictive means 7 may be a suitable die.

If it is desired to prepare an electrical cable that is insulation-bonded at spaced points, then constrictive means 7 can be mounted on an axle, not shown, which axle is adapted to move back and forth in a horizontal direction and thus break contact occasionally with the wire 6. Or if very light contact is maintained between the two wires then the natural vibrations of the wires will cause an occasional break in contact.

On leaving constrictive means 7 the wires 6 and 8 are in the form of an insulation bonded cable 11. The cable 11 then passes through a heating device 12 in which the plastic insulation on wire 6 is hardened.

As a further modification of Fig. l, the applicator pot 3 can be adapted to supply heat to the bath 4. In this case the bath 4 may consist of a thermoplastic resin such as the vinyl polymers. The wires 1 and 3 would pass to the constrictive means '7 as shown, or they could be contacted inside or below the heating device if desired. The cable 11 would not need to pass through a heating device 12 since bonding between the wires 6 and 8 would be effected merely by air cooling.

One of the greatest advantages of the present invention is that it allows the preparation in a simple and economical manner of electrical cable having the separate strands of wire coated in plastic insulation. can be readily accomplished by the dip-wipe method illustrated in Fig. 1. The batch 4 may be a viscous dispersion of polyvinyl chloride colored a deep red with a suitable pigment. This would result in the wire 6 being coated with a red plastic insulation. The wire 8 on the other hand may come from a dip-wipe device in which the bath is colored white. The cable 11 will then be composed of one white and one redwire. Thus, coding of wires is accomplished simply and easily without the use of complex dies or pressure systems. This is one of the outstanding advantages of the present invention. As pointed out earlier, the present invention is not limited to two wire cables. A cable may be built up of as This many wires as needed and each of them may have a difierent color.

Fig. 3 shows a device for making the electrical cable of the present invention in alternative apparatus. Here coated wires 13 and 14 have already been coated with a thermoplastic resin. Wire 13 passes through a heater 15 which serves to soften the thermoplastic resin insulation of wire 13. The heating may be carried out using steam, electricity, infrared, olf gases, or any other convenient source of heat. The two wires 13 and 14 then pass to constrictive means 7 which may be below or in side the heater 15 and which forces the two wires into close physical contact. The resulting cable 11 may then be merely air-cooled to yield an insulation bonded electrical cable. The plastic insulation on wires 13 and 14 may be of different colors in order to yield a coded cable. It may sometimes be desirable to pass wire 14 through the heater 15 in order that its insulation too may be softened.

In Fig. 4 there are illustrated the cross sections of a duplex cable prepared by the process of the present invention. Fig. 4a illustrates the cross section of a duplex cable wherein the insulation of one of the strands of insulated wire is in a tacky condition when it is contacted with the non-tacky insulation of the other wire. Such a cable may be readily separated by hand into two individual strands of insulated wire for the purpose of making electrical connections so long as the cable was formed by gentle contact between the two insulated wires; stronger contact between the two wires when the insulation on one wire was in a tacky condition results in a stronger bond. One of the advantages of the present invention is that the strength of the bond between the two wires may be controlled by varying the force with which the two wires are brought into contact to form the cable. Fig. 4b illustrates the separated ends of such a cable in cross-sectional view. Another of the surprising advantages of this cable is that the user of such a cable can readily identify which wire is which even in the dark. By separating the two strands and feeling them with the fingers the user can easily determine which strand is perfectly round and symmetrical and which strand has the half-moon shaped groove 16. Thus duplex cables of the present invention can be coded not merely by color for the eye to see, but also by shape for the fingers to feel. Fig. illustrates a duplex cable wherein the insulation on each of the separate strands of wire was in a tacky condition when the wires were brought into contact. This type of cable can only be coded by color and not by shape as in Fig. 4. Fig. 6 illustrates a 4-wire cable in which the insulation on two of the strands was in a nontacky condition when contacted with the other two wires whose insulation was in a tacky condition. It is obvious that many more individual strands of insulated wire could be built up around the four strands illustrated in Fig. 6. Any number of insulated wires may be attached side by side to adjacent wires in a single layered, multi-layered, or coaxial relationship by the process of the present invention.

It should be noted that cables prepared by the present invention all have one thing in common: there is a line of demarcation, a joint 17 at the point of adherence between any two adjacent insulated wires. This joint 17 results from the fact that the plastic insulation on any strand of wire is never rendered sufiiciently soft so as to flow into, and merge with, the plastic insulation on any other strand of' wire. The plastic insulation is merely rendered or deposited tacky, sticky, so that one insulated wire will stick to another when the two wires are brought into contact. The joint 17 results from the fact that the tacky plastic insulation on one strand of wire conforms to the shape of theplastic insulation on a second strand of wire, whether or not the plastic insulation on the second strand istacky. I V

In making the cable as illustrated in Fig. 1, the wire 1 may be a naked wire or it may be one which is already coated with a braided or a plastic insulation of some kind. The nozzle 2 may be any device that will allow the wire 1 to pass through the path 4 and thus pick up a coating of whatever material is being used for the plastic insulation. Although it is preferred that the bath 4 be composed of a viscous dispersion of polyvinyl chloride it may be composed of any other resinous compositions suitable for the preparation of coatings as for example, acrylic ester polymers, polyvinyl acetals, styrenated alkyds, styrene-butadiene, or the phenolic or urea derivatives. The bath material is generally what is known as an organosol or plastisol. Organosols and plastisols are dispersions of resins and/or resinous polymers along with modifying ingredients in non-aqueous media. A typical organosol is as follows:

Parts by weight Polymer: Polyvinyl chloride 37 Plasticizer: Di-2-ethyl hexyl phthalate 15 Solvent: Methyl-isobutyl-ketone 5 Stabilizer: Lead silicate 3 Lubricant: Lead stearate 2 Swelling agent: Xylene 10 Surfactant: Polyethylene glycol monolaurate 2 Colorant: Titanium dioxide 3 Filler: Calcium carbonate 8 Diluent: Kerosene 15 The various modifying agents as well as the principal polymer may be widely varied within the skill of those familiar with the art. Enamels, latexes, and lacquers may also be used as the bath.

In Fig. 1 Wire 8 has already been covered with a braided insulation or a curved or dried plastic insulation, or both. However, instead of passing through the channel 9, wire 8 may pass through a nozzle similar to nozzle 2 and into the bath 4. With this modification, wire 6 and wire 8 would both have a coating of wet plastic insulation just before being brought into contact. The pulley 10 would be eliminated since the wire 8 would pass through a die similar to die 5 before passing to the contacting or constrictive means 7. 1

The insulation bonded cable may be used for any electrical or electronic application where cable protected by insulation is suitable. Such cables find use as the legwires of electric detonators and ignitors; In the electronic industry the cables find use as television rotor control cables.

We claim:

l. A method of producing electrical cable composed of a plurality of individual strands of insulated wire, said method comprising: depositing plastic insulation on separate wires from a liquid suspension of said plastic to form coated wires; contacting together said wires, at least a portion of the total of said wires having said plastic insulation in a still uncured tacky condition, and curing said uncured coating whereby an insulation-bonded cable is produced.

2. A method according to claim 1 wherein said insulated wires are contacted together throughout their entire length.

3. A method of producing electrical cable composed of two strands of insulated wire, said method comprising: depositing plastic insulation on each of two separate wires from a liquid suspension of said plastic to form coated wires; contacting together said coated wires, at least one of which being coated with plastic insulation in a still uncured tacky condition, and curing said uncured coating whereby an insulation-bonded cable is produced.

4. A method of producing insulation-bonded electrical cable composed of two strands of insulated wire, said method comprising: depositing uncured plastic insulation from a liquid suspension of said plastic on two separate strands of wire to form coated wires; curing said plastic insulation on one of said coated wires to form a dry,

5 flexible, continuous, coating thereon; contacting together said wire having a cured plastic insulation coating and the wire having an uncured plastic insulation coating; and thereafter treating the resulting cable to produce a dry, flexible and continuous coating on said wire having an uncured plastic insulation coating.

5. A method according to claim 4 in which said two wire are contacted together for their entire lengths.

6. A method according to claim 3 wherein said plastic insulation on said two wires is of a different color, each from the other.

7. A method of producing electrical cable composed of four strands of insulated wire, said method comprising: depositing plastic insulation from a liquid suspension of said plastic on each of four separate wires to form coated wires; contacting together said coated wires, at least two of which are still coated with a plastic insulation in an uncured tacky condition, and curing the remaining uncured plastic coating whereby an insulationbonded cable is produced.

References Cited in the file of this patent UNITED STATES PATENTS 

3. A METHOD OF PRODUCING ELECTRICAL CABLE COMPOSED OF TWO STRANDS OF INSULATED WIRE, SAID METHOD COMPRISING: DEPOSITING PLASTIC INSULATION ON EACH OF TWO SEPARATE WIRES FROM A LIQUID SUSPENSION OF SAID PLASTIC TO FORM COATED WIRES, CONTACTING TOGETHER SAID COATED WIRES, AT LEAST ONE 